Spin-coated Ga-doped ZnO transparent conducting thin films for organic light-emitting diodes

Gallium doped zinc oxide (GZO) thin films have been prepared by a simple sol-gel spin coating technique. XRD results showed the preferential c-axis orientation of the crystallites and the presence of the wurtzite phase of ZnO. A lowest resistivity of 3.3 x 10-3 Ω cm was obtained for the ZnO film doped with 2 at% of Ga after post-annealing at 500 deg. C for 45 min in a H2 atmosphere. All the films showed more than 80% of transparency in the entire visible region. Blue shifting of the optical band gap was observed with an increase in Ga doping, which can be explained on the basis of the Burstein-Moss effect. OLED devices were fabricated using 2 at% Ga-doped ZnO thin films as anodes. Preliminary results obtained demonstrated that spin-coated GZO films can be used as a promising TCO for optoelectronic device applications.